I'm trying to bulk update visibility of all products from Actions > Update Attributes under Catalog > Products menu.
I'm getting this error. Any Idea Why?
I just encountered this issue, which turned out to be caused by the Ebizmarts_MailChimp extension.
It has been fixed in a recent commit, but has yet to be added to a release. https://github.com/mailchimp/mc-magento/issues/209